The delivery of nucleic acids to cells, particularly but not exclusively, in gene therapy, has many applications in the medical and scientific fields. For example, gene therapy may be used to introduce replacement genes, thereby correcting genetic defects, or to introduce therapeutic genes to specific cells. Delivery of nucleic acids that mediate RNA interference is another way to influence gene expression and treat disease.
Numerous techniques have been developed to introduce DNA into cells. Functional exogenous genes can be introduced to mammalian cells in vitro by a variety of physical methods, including transfection, direct microinjection, electroporation, and coprecipitation with calcium phosphate. Most of these techniques, however, are impractical for delivering genes to cells within intact animals. Therefore, viruses are typically used as carriers for a transgene. However, using viruses as carriers is not desirable since problems of immunogenicity, cytotoxicity, and insertional mutagenesis are associated with viral vectors. Consequently, efficient nonviral nucleic acid delivery systems are needed.